[THIN] Re: Redundant Web interface for PNAgent
- From: "Jeff Durbin" <techlists@xxxxxxxxxxxxx>
- To: <thin@xxxxxxxxxxxxx>
- Date: Mon, 26 Jul 2004 10:23:03 +1200
I just tested this. I created two DNS records, each called 'test', one
with 192.168.1.90, and one with 192.168.1.95. Both addresses were for valid
machines that were up. I then went to a different machine and did an
NSLOOKUP on 'test'. I got both IP addresses back, so Frank is correct: the
DNS query does return all addresses that are vaild for the host name.
I then pinged 'test' from the third machine. The host name resolved to
192.168.1.95 and pinged successfully.
I then shut down 192.168.1.95 and went back to the third machine. I pinged
'test'. It still chose 192.168.1.95, but since the machine was down, it
couldn't successfully ping it. I continued to reinitiate the ping command
for about 5 minutes, and it always failed, as it was always trying to ping
192.168.1.95. Presumably, Chris is correct that the record's TTL has to
expire.
I then flushed the DNS cache on machine 3 and tried again - still resolved
to 192.168.1.95 and wouldn't ping.
I then deleted the two 'test' records, set the server's default TTL to 5
seconds, recreated the records, flushed the DNS resolver cache on machine 3,
and pinged again. I still got 192.168.1.95, which wouldn't ping, even after
30 seconds.
So, the DNS server does return all addresses for the host name, but it
still doesn't seem to 'failover' to a different IP if the first one is no
good. BTW, this is all Win2K.
JD
> -----Original Message-----
> From: thin-bounce@xxxxxxxxxxxxx
> [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf Of Frank Monroe
> Sent: Monday, 26 July 2004 9:25 a.m.
> To: 'thin@xxxxxxxxxxxxx'
> Subject: [THIN] Re: Redundant Web interface for PNAgent
>
> Ok, let me explain this another way, the PNAgent will behave
> just like your browser. For example, when you use your
> browser to go to www.microsoft.com, your browser is given the
> following IP address list to connect:
> 207.46.250.222, 207.46.156.156, 207.46.156.220,
> 207.46.156.252, 207.46.245.156, 207.46.144.222,
> 207.46.250.252, 207.46.244.188. The order may be different
> due to the round robin. Your browser will first attempt to
> contact the web server with the first address listed. If it
> fails, it will try the second and the others on the list
> until it find one that succeeds.
> It will continue to use the IP address that succeeds until it
> fails in which case it will try the list again.
>
> -----Original Message-----
> From: Chris Lynch [mailto:lynch00@xxxxxxx]
> Sent: Sunday, July 25, 2004 5:02 PM
> To: thin@xxxxxxxxxxxxx
> Subject: [THIN] Re: Redundant Web interface for PNAgent
>
>
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Within the PNAgent config. He was asking how to provide
> uptime for his
> clients if the WI server were ever to go down. DNS
> Round-Robin does not
> provide redundancy to the clients. I.E. You have two
> records with the same
> name: WI.COMPANY.COM resolving to 1.1.1.1 and 1.1.1.2. If
> CLIENTA gets the
> IP address resolution 1.1.1.1 and that server crashes,
> reboots, or becomes
> unavailable, the client workstation is not going to re-query
> for the DNS
> record unless the TTL expires. If the TTL does expire, the
> client has a
> 50/50 chance of getting the IP Address of the server that is online.
>
> To provide a way for complete uptime, you will need to NLB
> the web servers.
>
> What you were referring to was the MF server list within the
> PNAgent Admin
> page.
>
> Chris
>
>
> > -----Original Message-----
> > From: thin-bounce@xxxxxxxxxxxxx
> > [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf Of Frank Monroe
> > Sent: Sunday, July 25, 2004 1:18 PM
> > To: 'thin@xxxxxxxxxxxxx'
> > Subject: [THIN] Re: Redundant Web interface for PNAgent
> >
> > This is how we have ours setup, DNS round robin. I just
> > tested it. And it does work. If any of the servers in the
> > IP address list are down, it simply tries another in the list
> > until it find one that works. You don't have to use NLB if
> > you don't want to.
> >
> > -----Original Message-----
> > From: Chris Lynch [mailto:lynch00@xxxxxxx]
> > Sent: Sunday, July 25, 2004 2:51 PM
> > To: thin@xxxxxxxxxxxxx
> > Subject: [THIN] Re: Redundant Web interface for PNAgent
> >
> >
> >
> > *** PGP SIGNATURE VERIFICATION ***
> > *** Status: Bad Signature
> > *** Alert: Signature did not verify. Message has been altered.
> > *** Signer: Chris Lynch <lynch00@xxxxxxx> (0x6AE53DCC)
> > *** Signed: 7/25/2004 11:50:56 AM
> > *** Verified: 7/25/2004 1:57:30 PM
> > *** BEGIN PGP VERIFIED MESSAGE ***
> >
> > DNS Aliasing (or more commonly referred to as "Round Robin
> > DNS") provides no
> > failover what-so-ever. If you need failover, you will need
> > NLB (either the
> > MS product or a hardware device).
> >
> > Chris
> >
> >
> > ________________________________
> >
> > From: thin-bounce@xxxxxxxxxxxxx
> > [mailto:thin-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Frank Monroe
> > Sent: Saturday, July 24, 2004 2:43 PM
> > To: 'thin@xxxxxxxxxxxxx'
> > Subject: [THIN] Re: Redundant Web interface for PNAgent
> >
> >
> > Build two web servers with pnagent and then set your
> > dns alias for
> > pnagent to point to both IP addresses. You can also use network
> > load balancing.
> >
> > -----Original Message-----
> > From: King, Jesse [mailto:JKing@xxxxxxxxxxxxxxxxxxx]
> > Sent: Thursday, July 22, 2004 9:47 AM
> > To: thin@xxxxxxxxxxxxx
> > Subject: [THIN] Redundant Web interface for PNAgent
> >
> >
> > Is there a way to have fail-over web interface
> > for PNAgent?
> >
> > Situation -
> >
> > 5 server farm, plus separate server running the Web
> Interface admin
> > where PNAgent picks up all its config information.
> >
> > If that separate server goes down for some
> > reason, then so
> > do the
> > users icons....
> >
> > Any thoughts?
> >
> >
> >
> >
> > *** END PGP VERIFIED MESSAGE ***
> >
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>
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> Using the latest software, hardware, networking technologies,
> proven technical expertise, proprietary software and best
> practices, EOL provides custom-tailored solutions for each
> client's mission and specific goals.
> http://www.go-eol.com
> **********************************************************
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Using the latest software, hardware, networking technologies, proven technical
expertise, proprietary software and best practices, EOL provides
custom-tailored solutions for each client?s mission and specific goals.
http://www.go-eol.com
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